1. Field of the Invention
This invention relates to an inspecting apparatus for a glass substrate to inspect whether a surface of a substrate is defective or not with naked eyes.
2. Related Art
In general, in fabricating a large-scale substrate such as semiconductor wafer or a liquid crystal display (LCD), a plasma display panel (PDP), an organic electro-luminescence display, and the like, the displays are inspected with naked eyes to detect debris, spots, or blurs that may remain on the substrates. In this case, an illumination device that uniformly illuminates the entirety of the substrate is used to facilitate detection of defects. The configuration of the related art inspecting apparatus for a glass substrate will now be described.
FIG. 1a is a view schematically showing the related art inspecting apparatus for a glass substrate, and FIG. 1b is a view substantially illustrating detection of light reflected by an upper illumination unit by an inspector.
First, with reference to FIG. 1a, the related art inspecting apparatus for a glass substrate comprises an upper illumination unit 30 and a rear illumination unit 40 which are, respectively, disposed at an upper side and a rear side of a glass substrate 10, an inspection target. An inspector 50 detects a defect of the glass substrate 10 by means of a reflective light L1 irradiated from the upper illumination unit 30 and a transmissive light L2 irradiated from the rear illumination unit 40. The glass substrate 10 is fixed by clampers 20 and comprises pattern regions such as a color filter region, a column spacer region, a pixel region, etc. formed on a front surface thereof. The inspector 50 is in front of the glass substrate 10 and checks whether the front surface of the glass substrate 10 is defective or not.
As shown in FIG. 1b, the upper illumination unit 30 comprises a light source 31, a reflecting unit 32, a condensing unit 33, and a scattering (diffusion) unit 34. When light is first generated from the light source 31, it is reflected to the condensing unit 33 by means of the reflecting unit 32, transmitted through the condensing unit 33 and the scattering unit 34, and then irradiated to the glass substrate 10, the inspection target. The light reflected by the glass substrate 10 proceeds to the naked eyes of the inspector 50. Then, the inspector 50 observes the reflected light to check whether the glass substrate 10 is defective or not.
The inspecting method is performed such that mura, namely, blurs, present on the glass substrate 10 is checked by the naked eyes of the inspector based on the difference between the strength and a reflection angle of light reflected from a flawless surface of the glass substrate 10 and those of light reflected from a defective surface of the glass substrate 10. However, the related art inspecting apparatus for the glass substrate has a problem in that, actually, it is not easy to properly inspect the glass substrate 10 because of the difference in thickness of pigments or an overlay in forming color filters. Namely, the pigments for forming red, green, and blue color filters, column spacers, or pixels of a TFT substrate make it difficult to detect blurs, such as overlay blurs, namely, butterfly blurs, that affect the characteristics of the viewing angle. For instance, the butterfly blurs can be detected, provided two or more layers are stacked, so after all the follow-up layer processes are performed, the butterfly blurs are inspected. In other words, the butterfly blurs cannot be detected until the follow-up layer processes are performed, resulting in a loss of production because the follow-up processes should be necessarily performed.
In an effort to solve this problem, pigments were formed or a pixel layered pattern was formed on a metal-deposited glass substrate and then a sampling inspection was performed. However, in case of using the metal-deposited glass substrate such as a TFT gate pattern, the blurs with respect to the pixels, the column spacers or the pigments of the color filters can be well seen, but disadvantageously, the sampling and the glass substrate should be separately fabricated, causing much loss in terms of production and costs.